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We derive cosmological constraints on the matter density, , and the amplitude of fluctuations, , using , a catalog of 1800 galaxy clusters we identified in the Sloan Digital Sky Survey-DR13 spectroscopic data set using our GalWeight technique to determine cluster membership. By analyzing a subsample of 756 clusters in a redshift range of 0.045 ≤ z ≤ 0.125 and virial masses of M ≥ 0.8 × 1014 with mean redshift of z = 0.085, we obtain (systematic) and (systematic), with a cluster normalization relation of. There are several unique aspects to our approach: we use the largest spectroscopic data set currently available, and we assign membership using the GalWeight technique, which we have shown to be very effective at simultaneously maximizing the number of bona fide cluster members while minimizing the number of contaminating interlopers. Moreover, rather than employing scaling relations, we calculate cluster masses individually using the virial mass estimator. Since is a low-redshift cluster catalog we do not need to make any assumptions about evolution either in cosmological parameters or in the properties of the clusters themselves. Our constraints on and are consistent and very competitive with those obtained from non-cluster abundance cosmological probes such as cosmic microwave background, baryonic acoustic oscillation (BAO), and supernovae. The joint analysis of our cluster data with Planck18+BAO+Pantheon gives and. [ABSTRACT FROM AUTHOR]

Making cosmological inferences from the observed galaxy clustering requires accurate predictions for the mean clustering statistics and their covariances. Those are affected by cosmic variance – the statistical noise due to the finite number of harmonics. The cosmic variance can be suppressed by fixing the amplitudes of the harmonics instead of drawing them from a Gaussian distribution predicted by the inflation models. Initial realizations also can be generated in pairs with 180○ flipped phases to further reduce the variance. Here, we compare the consequences of using paired-and-fixed versus Gaussian initial conditions on the average dark matter clustering and covariance matrices predicted from N -body simulations. As in previous studies, we find no measurable differences between paired-and-fixed and Gaussian simulations for the average density distribution function, power spectrum, and bispectrum. Yet, the covariances from paired-and-fixed simulations are suppressed in a complicated scale- and redshift-dependent way. The situation is particularly problematic on the scales of Baryon acoustic oscillations where the covariance matrix of the power spectrum is lower by only |$\sim 20{{\ \rm per\ cent}}$| compared to the Gaussian realizations, implying that there is not much of a reduction of the cosmic variance. The non-trivial suppression, combined with the fact that paired-and-fixed covariances are noisier than from Gaussian simulations, suggests that there is no path towards obtaining accurate covariance matrices from paired-and-fixed simulations – result, that is theoretically expected and accepted in the field. Because the covariances are crucial for the observational estimates of galaxy clustering statistics and cosmological parameters, paired-and-fixed simulations, though useful for some applications, cannot be used for the production of mock galaxy catalogues. [ABSTRACT FROM AUTHOR]

Any successful model of galaxy formation needs to explain the low rate of star formation in the small progenitors of today's galaxies. This inefficiency is necessary for reproducing the low stellar-to-virial mass fractions, suggested by current abundance matching models. A possible driver of this low efficiency is the radiation pressure exerted by ionizing photons from massive stars. The effect of radiation pressure in cosmological, zoom-in galaxy formation simulations is modelled as a non-thermal pressure that acts only in dense and optically thick star-forming regions. We also include photoionization and photoheating by massive stars. The full photoionization of hydrogen reduces the radiative cooling in the 104-4.5 K regime. The main effect of radiation pressure is to regulate and limit the high values of gas density and the amount of gas available for star formation. This maintains a low star formation rate of ∼1 M⊙ yr−1 in haloes with masses about 1011 M⊙ at z ≃ 3. Infrared trapping and photoionization/photoheating processes are secondary effects in this mass range. The galaxies residing in these low-mass haloes contain only ∼0.6 per cent of the total virial mass in stars, roughly consistent with abundance matching. Radiative feedback maintains an extended galaxy with a rising circular velocity profile. [ABSTRACT FROM AUTHOR]

ABSTRACT We study the concentration of dark matter haloes and its evolution in N-body simulations of the standard Λ cold dark matter (ΛCDM) cosmology. The results presented in this paper are based on four large N-body simulations with ∼10 billion particles each: the Millennium-I and -II, Bolshoi and MultiDark simulations. The MultiDark (or BigBolshoi) simulation is introduced in this paper. This suite of simulations with high mass resolution over a large volume allows us to compute with unprecedented accuracy the concentration over a large range of scales (about six orders of magnitude in mass), which constitutes the state of the art of our current knowledge on this basic property of dark matter haloes in the ΛCDM cosmology. We find that there is consistency among the different simulation data sets, despite the different codes, numerical algorithms and halo/subhalo finders used in our analysis. We confirm a novel feature for halo concentrations at high redshifts: a flattening and upturn with increasing mass. The concentration c( M, z) as a function of mass and the redshift and for different cosmological parameters shows a remarkably complex pattern. However, when expressed in terms of the linear rms fluctuation of the density field σ( M, z), the halo concentration c(σ) shows a nearly universal simple U-shaped behaviour with a minimum at a well-defined scale at σ∼ 0.71. Yet, some small dependences with redshift and cosmology still remain. At the high-mass end (σ < 1), the median halo kinematic profiles show large signatures of infall and highly radial orbits. This c-σ( M, z) relation can be accurately parametrized and provides an analytical model for the dependence of concentration on halo mass. When applied to galaxy clusters, our estimates of concentrations are substantially larger - by a factor up to 1.5 - than previous results from smaller simulations, and are in much better agreement with results of observations. [ABSTRACT FROM AUTHOR]

Lambda Cold Dark Matter (ACDM) is now the standard theory of structure formation in the universe. We present the first results from the new Bolshoi dissipationless cosmological ACDM simulation that uses cosmological parameters favored by current observations. The Bolshoi simulation was run in a volume 250 h-1 Mpc on a side using ∼8 billion particles with mass and force resolution adequate to follow subhalos down to the completeness limit of Vcirc = 50 km s-1 maximum circular velocity. Using merger trees derived from analysis of 180 stored time steps we find the circular velocities of satellites before they fall into their host halos. Using excellent statistics of halos and subhalos (∼10 million at every moment and ∼50 million over the whole history) we present accurate approximations for statistics such as the halo mass function, the concentrations for distinct halos and subhalos, the abundance of halos as a function of their circular velocity, and the abundance and the spatial distribution of subhalos. We find that at high redshifts the concentration falls to a minimum value of about 4.0 and then rises for higher values of halo mass--a new result. We present approximations for the velocity and mass functions of distinct halos as a function of redshift. We find that while the Sheth-Tormen (ST) approximation for the mass function of halos found by spherical overdensity is quite accurate at low redshifts, the ST formula overpredicts the abundance of halos by nearly an order of magnitude by ɀ = 10. We find that the number of subhalos scales with the circular velocity of the host halo as Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed., and that subhalos have nearly the same radial distribution as dark matter particles at radii 0.3-2 times the host halo virial radius. The subhalo velocity function N(> Vsub) scales as Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed.. Combining the results of Bolshoi and Via Lactea-II simulations, we find that inside the virial radius of halos with Vcirc = 200 km s-1 the number of satellites is N(> Vsub) = (Vsub/58km s-1)-3 for satellite circular velocities in the range 4 km s-1 < Vsub < 150 km s-1. [ABSTRACT FROM AUTHOR]

In current and future surveys, quasars play a key role. The new data will extend our knowledge of the Universe as it will be used to better constrain the cosmological model at redshift z > 1 via baryon acoustic oscillation and redshift space distortion measurements. Here, we present the first clustering study of quasars observed by the extended Baryon Oscillation Spectroscopic Survey. We measure the clustering of ~70 000 quasars located in the redshift range 0.9 < z < 2.2 that cover 1168 deg2. We model the clustering and produce highfidelity quasar mock catalogues based on the BigMultiDark Planck simulation. Thus, we use a modified (sub)halo abundance matching model to account for the specificities of the halo population hosting quasars.We find that quasars are hosted by haloes with masses~1012.7M☉ and their bias evolves from 1.54 (z = 1.06) to 3.15 (z = 1.98). Using the current extended Baryon Oscillation Spectroscopic Survey data, we cannot distinguish between models with different fractions of satellites. The high-fidelity mock light-cones, including properties of haloes hosting quasars, are made publicly available. [ABSTRACT FROM AUTHOR]

In current and future surveys, quasars play a key role. The new data will extend our knowledge of the Universe as it will be used to better constrain the cosmological model at redshift z > 1 via baryon acoustic oscillation and redshift space distortion measurements. Here, we present the first clustering study of quasars observed by the extended Baryon Oscillation Spectroscopic Survey. We measure the clustering of ~70 000 quasars located in the redshift range 0.9 < z < 2.2 that cover 1168 deg2. We model the clustering and produce highfidelity quasar mock catalogues based on the BigMultiDark Planck simulation. Thus, we use a modified (sub)halo abundance matching model to account for the specificities of the halo population hosting quasars. We find that quasars are hosted by haloes with masses~1012.7M☉ and their bias evolves from 1.54 (z = 1.06) to 3.15 (z = 1.98). Using the current extended Baryon Oscillation Spectroscopic Survey data, we cannot distinguish between models with different fractions of satellites. The high-fidelity mock light-cones, including properties of haloes hosting quasars, are made publicly available. [ABSTRACT FROM AUTHOR]

Current and future large redshift surveys, as the Sloan Digital Sky Survey IV extended Baryon Oscillation Spectroscopic Survey (SDSS-IV/eBOSS) or the Dark Energy Spectroscopic Instrument (DESI), will use emission-line galaxies (ELGs) to probe cosmological models by mapping the large-scale structure of the Universe in the redshift range 0.6 < z < 1.7. With current data, we explore the halo-galaxy connection by measuring three clustering properties of g-selected ELGs as matter tracers in the redshift range 0.6 < z < 1: (i) the redshift-space two-point correlation function using spectroscopic redshifts from the BOSS ELG sample and VIPERS; (ii) the angular two-point correlation function on the footprint of the CFHT-LS; (iii) the galaxy-galaxy lensing signal around the ELGs using the CFHTLenS. We interpret these observations by mapping them on to the latest high-resolution MultiDark Planck N-body simulation, using a novel (Sub)Halo-Abundance Matching technique that accounts for the ELG incompleteness. ELGs at z ~ 0.8 live in haloes of (1 ± 0.5) × 1012 h-1M☉ and 22.5 ± 2.5 per cent of them are satellites belonging to a larger halo. The halo occupation distribution of ELGs indicates that we are sampling the galaxies in which stars form in the most efficient way, according to their stellar-to-halo mass ratio. [ABSTRACT FROM AUTHOR]

Future dark energy experiments will require accurate theoretical predictions for the baryon acoustic oscillations (BAOs). Here, we use large N-body simulations to study any systematic shifts and damping in BAO due to non-linear effects. The impact of cosmic variance is largely reduced by dividing the tracer power spectrum by that from a 'BAO-free' simulation starting with the same random amplitudes and phases. The accuracy of our simulations allows us to resolve well dark matter (sub)haloes, which permits us to study with high accuracy (better than 0.02 per cent for dark matter and 0.07 per cent for low-bias haloes) small BAO shifts α towards larger k, and non-linear damping Σnl of BAO in the power spectrum. For dark matter, we provide an accurate parametrization of the evolution of α as a function of the linear growth factor D(z). For halo samples, with bias from 1.2 to 2.8, we measure a typical BAO shift of ≈0.25 per cent, with no appreciable evolution with redshift. Moreover, we report a constant shift as a function of halo bias. We find a different evolution of the BAO damping in all halo samples as compared to dark matter with haloes suffering less damping, and also find some weak dependence on bias. Larger BAO shift and damping are measured in redshift-space, which can be explained by linear theory due to redshift-space distortions. A clear modulation in phase with the acoustic scale is observed in the scale-dependent halo bias due to the presence of BAOs. We compare our results with previous works. [ABSTRACT FROM AUTHOR]

We investigate the origin and evolution of fossil groups in a concordance ΛCDM cosmological simulation. We consider haloes with masses between and , and study the physical mechanisms that lead to the formation of the large gap in magnitude between the brightest and the second most bright group member, which is typical for these fossil systems. Fossil groups are found to have high dark matter concentrations, which we can relate to their early formation time. The large magnitude gaps arise after the groups have built up half of their final mass, due to merging of massive group members. We show that the existence of fossil systems is primarily driven by the relatively early infall of massive satellites, and that we do not find a strong environmental dependence for these systems. In addition, we find tentative evidence for fossil group satellites falling in on orbits with typically lower angular momentum, which might lead to a more efficient merger on to the host. We find a population of groups at higher redshifts that go through a ‘fossil phase’: a stage where they show a large magnitude gap, which is terminated by renewed infall from their environment. [ABSTRACT FROM AUTHOR]

We present a statistical analysis of voids in the two-degree Field Galaxy Redshift Survey (2dFGRS). In order to detect the voids, we have developed two robust algorithms. We define voids as non-overlapping maximal spheres empty of haloes or galaxies with mass or luminosity above a given value. We search for voids in cosmological N-Body simulations to test the performance of our void finders. We obtain and analyse the void statistics for several volume-limited samples for the North Galactic Pole (NGP) and the South Galactic Pole (SGP) constructed from the 2dFGRS full data release. We find that the results obtained from the NGP and the SGP are statistically compatible. From the results of several statistical tests we conclude that voids are essentially uncorrelated, with at most a mild anticorrelation and that at the 99.5 per cent confidence level there is a dependence of the void number density on redshift. We develop a technique to correct the distortion caused by the fact that we use the redshift as the radial coordinate. We calibrate this technique with mock catalogues and find that the correction might be of some relevance to carry out accurate inferences from void statistics. We study the statistics of the galaxies inside nine nearby voids. We find that galaxies in voids are not randomly distributed: they form structures like filaments. We also obtain the galaxy number density profile in voids. This profile follow a similar but steeper trend to that followed by haloes in voids. [ABSTRACT FROM AUTHOR]